Effect of Current Density on the Wear Resistance of Ni–P Alloy Coating Prepared through Immersion-Assisted Jet-Electrodeposition

To improve the wear resistance of 45 steel surfaces, a Ni−P alloy coating was prepared on the surface of 45 steel with an immersion-assisted jet-electrodeposition technology. Scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and confocal microscopy were used in testing the surface morphology, composition, structure, grain size, and wear scar parameters of the coating. The effect of immersion-assisted jet-electrodeposition on the wear resistance of Ni−P alloy coating at current densities of 20–60 A·cm−2 were explored and analyzed. Results showed that the surface quality, microhardness, and wear resistance of Ni−P alloy coatings prepared through immersion-assisted jet-electrodeposition were improved compared with those of the coatings prepared through traditional jet-electrodeposition. With the increase in the current density, the surface cell structure of the alloy coating was refined, the flatness was improved, the surface Ni content was increased, the grain size was refined, and the coating thickness, the microhardness, and wear resistance showed a trend of first increasing and then decreasing. The best surface quality of the coating was observed at a current density of 50 A·cm−2. Moreover, the unit cell structure was obvious, the surface was flat and dense, the coating thickness was the largest, reaching 21.42 μm, the highest Ni content was obtained (98.25 wt.%), the smallest grain size (6.6 nm) was obtained, the microhardness of the coating reached a maximum value (725.58 HV0.1), and the best wear resistance was observed.